To recap, ScaleIO's ECS (Elastic Converged Storage) software turns a server's direct-attached storage (DAS) into a shared SAN (storage area network). ECS is, in effect a Virtual Storage Appliance (VSA) and so in the same product class as HP's software-only StoreVirtual product. The software in the old LeftHand iSCSI SAN controller has been made available on its own; just add a server to create a SAN.

Multiple servers - in fact, thousands, according to ScaleIO - can be clustered in the virtual SAN (VSAN) to provide more capacity and more I/O performance as each server plays its part in the VSAN's overall I/O task. The VSAN can be dynamically scaled up or down. We note that this is obviously a variant of software-defined storage.

Returning to the land of hardware, the server-attached storage can be disk or flash-based - either PCIe or SSD, or both, El Reg guesses - and ECS supports x86 and ARM processors, and various chipsets, which magnifies EMC's opportunity to offer VSA products.

This is a granular way of building SANs by scaling up at the server and DAS level. We envisage a cloud provider of compute and storage or VSAN storage having racks filled with 1U or 2U servers with DAS, and dynamically configuring them to provision customers wanting compute plus storage or block-access storage-only services.

Customers run a lightweight Data Server (DS) driver on any node that contains DAS Flash that you want to add to a virtual pool, and a Data Client (DC) driver on any node that should have access to the virtual pool. Of course, customers can run both the DS and DC code on a node that both contributes storage to a pool and needs access to the pool.

With ECS as the foundation, EMC can build out a scale-out server stack for a wide variety of use cases like VDI, virtualisation, databases, and HPC…in several target markets. For example, we can provide elastic, dynamic and flexible Flash storage to service provider partners who provide public cloud to their customers.

He adds this nugget: "Over time we will build in additional enterprise features so that advanced data services can be delivered irrespective of the underlying hardware."

Hussain talks about EMC and ScaleIO in a video:

The acquisition is an all-cash transaction and the dollar amount is not being revealed. Previously El Reg's storage desk speculated about it as being in the $200m to $300m area. The ScaleIO team is joining EMC.

EMC states: "ScaleIO accelerates EMC's strategy to deliver Flash across the entire server and storage infrastructure." To that end ScaleIO will become part of EMC's flash product division, and the ECS software will be included in the XtremSW suite which is directed at server-installed PCIe flash cards; what was initially called VFCache.

Currently the suite includes XtremSW Cache, a deduplicating write-through cache supported on Windows, Linux and VMware. It provides cache coherency for Oracle RAC environments.

With this software, EMC can turn one or more flash-equipped servers into a flash SAN, which is similar to what Fusion-io's acquired ION Data Accelerator software does. The low-hanging fruit days of server-side flash are ending and suppliers are going to have to compete strongly for business. ®